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import numpy as np
from scipy.signal import convolve
def _ricker(points, a):
A = 2 / (np.sqrt(3 * a) * (np.pi**0.25))
wsq = a**2
vec = np.arange(0, points) - (points - 1.0) / 2
xsq = vec**2
mod = (1 - xsq / wsq)
gauss = np.exp(-xsq / (2 * wsq))
total = A * mod * gauss
return total
def _cwt(data, wavelet, widths, dtype=None, **kwargs):
# Determine output type
if dtype is None:
if np.asarray(wavelet(1, widths[0], **kwargs)).dtype.char in 'FDG':
dtype = np.complex128
else:
dtype = np.float64
output = np.empty((len(widths), len(data)), dtype=dtype)
for ind, width in enumerate(widths):
N = np.min([10 * width, len(data)])
wavelet_data = np.conj(wavelet(N, width, **kwargs)[::-1])
output[ind] = convolve(data, wavelet_data, mode='same')
return output
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